Electron correlation in atoms and molecules

Abstract

Using a modified Rayleigh-Schrödinger perturbation scheme, it is shown that the first order correction to the Hartree-Fock function due to electron correlation effects may be written as Σ i>j A(χ ijφ 1...φ i−1φ i+1...φ j−1φ j+1...φ N −φ 1...φ N ), where the φ's are the Hartree-Fock SCF orbitals, A is the antisymmetrization operator, χ ij is an antisymmetrized function of two coordinates. It is also shown that each pair function χ ij may be evaluated by a variational procedure.